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EGR - what is it, waht does it do?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 90K5, Apr 9, 2002.

  1. 90K5

    90K5 1/2 ton status

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    I think I've got an EGR problem, my check engine light comes on under acceleration, but goes off when I turn off the igntion, so I can' tcheck the codes...anyway I need to understand what EGR is and how it works to be able to fix it...anyone?
     
  2. kilroy

    kilroy Registered Member

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    The codes are stored in memory, you should not have any problem reading them, reguardless of if the light is on or off before you start. If you are not able to read the codes you have a faulty ECM
     
  3. The EGR is "Exhaust Gas Recirculation" and vacuum is used to open and close the diaphram in the EGR valve. I had a EGR code "32" on my 89 K5 and I replaced the vacuum solenoid that operates the EGR. It was $11.00 from GM. That didn't fix it. I took the EGR off the intake and tested it by lifting the diaphram up with my fingers and holding a finger over the vacuum port. If the diaphram falls while you are plugging off the vacuum port with your finger, then You have a bad EGR. My EGR valve had a "N" located on the top for negative bleedoff. If yours is the same then replace it with another EGR valve. Make sure that you get the same exact one or you will have the same problem. I got mine from a local wrecking yard for $20.00, but you can get one from GM for $57.00. The vacuum solenoid is the most common component to fail to cause the EGR code.
     
  4. 90K5

    90K5 1/2 ton status

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    After I posted I went and looked at it, took the EGR Valve off and cleaned it a little. The diaphram stays up if my finger is over the vacuum port, so its good. The problem may have been a vacuum line, there was one that was disconnected when I was puttign the EGR back on, but it may have happened when I took it off...we'll see.......
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    EGR is intended to blend combustion byproducts (think that would be the right term) in the incoming mix.
    EGR=Exhaust Gas Recirculation

    Correctly operating, it should only be "working" at a steady cruise. Contrary to popular belief, it doesn't hurt WOT nor idle, unless it is malfunctioning. Some symptoms of EGR problems are stalling on decel, rough idle, surging cruise, etc.

    A lot of times on chev motors (and small fords apparently) the valve gets all carboned up and just removal and cleaning sometimes solves the problem. If you can get to it, reach up under the "mushroom" head of the thing, and try pushing the diaphram in. Make sure it moves freely, and returns to the starting position.

    Pushing the diaphram in while its running will likely stall the motor.

    The "problem" with later ones if you aren't code scanning, is that there is so much that can govern them (temp sensor, vac switches, ECM, etc) that it may not be the EGR thats faulty, although it may not be working correctly due to other components failure. Earlier vehicles used JUST a vacuum line to a "timed" port on the carb, later on temp switch and timed port, and so on.
     
  6. NoSmog73

    NoSmog73 1/2 ton status

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    Also you can "jump" with a paperclip the two pins to give you the code that it has stored in memory ( It will fash a certain amount of times after the self check ) someone else can give ya the 2 pin holes to jump....( I don't remember which one's )
     
  7. 90K5

    90K5 1/2 ton status

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    the two pin holes are the ones on the right. I know that, I have the scanner you plug into the port so you don't have to do it the ghetto way. Anyway, after cleaning the valve, I took it out on the highway, and drove it hard, couldn' get the light to come on...which may not mean much. after putting the stock chip back in, the light slowed down coming on, but still came on...lets just hope........
     

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